> artificial methods would take a lot.

Mars is orange because of rust. Turn the rust back to iron, magnetize it, and point all the magnets the same way. No energy required to maintain.

The core of Mars is about 1500 km down from the surface. The mantle density is about 3.5 tons per cubic meter, which at Mars gravity produces a rock pressure of 13 MegaPascals (MPa) per km. Basalt, which is volcanic rock that Mars has lots of, has a maximum compressive strength of 338 MPa. So by the time you get 26 km down, the rock will definitely fail and your drill hole will collapse.

The best steel has about 5 times the strength, but 2.2 times the density. So if you use it to line a drill hole, it will collapse under its own weight at 58 km. You are now 3.9% of the way to the core. The core is out of reach with known technology, so forget doing anything to it.